As one example, an outer-rotor DC brushless motor used as the driving apparatus of a vehicle air-conditioner will now be described.
A fan is attached to one end of a motor shaft and the other end of the motor shaft passes through a bearing portion (“housing”) and is inserted into a substrate-protecting case. A stator is assembled on the bearing portion. A rotor, constructed with a cup-shaped rotor yoke attached to the motor shaft that is rotatably supported by the bearing portion and with magnets attached to an inner circumferential surface of the rotor yoke, is assembled so as to surround the stator.
Also, a sensor magnet is provided on the other end of the motor shaft. The magnetic poles of the sensor magnet are detected by a Hall element mounted on the circuit substrate provided inside the substrate-protecting case so that an excitation current supplied to the motor coil can be switched.
An attachment protruding portion is erected on an end portion of the bearing portion that extends close to the top of the substrate-protecting case. This attachment protruding portion is integrally assembled on the substrate-protecting case with a ring-shaped first rubber vibration insulator positioned and fitted onto a ring-shaped protrusion provided on the substrate-protecting case, a ring-shaped second rubber vibration insulator placed upon the attachment protruding portion, and with a metal ring placed on the second rubber vibration insulator and screwed down. By doing so, vibration of the motor shaft is absorbed by the first and second rubber vibration insulators. This prevents vibration from being transmitted to the substrate-protecting case, which protects the wiring connections on the circuit substrate.
As the first and second rubber vibration insulators described above, butyl rubber (IIR), ethylene-propylene rubber (EPDM) or the like with a hardness of around 40 to 60 as measured by a rubber hardness gauge (JIS K 6253 (ISO 7619); durometer, type A, spring-type) is used (see Patent Document 1).
Patent Document 1
Japanese Laid-Open Patent Publication No. 2000-217324